package hot100;

public class mergeTwoLists {

    public mergeKLists.ListNode mergeTwoLists2(mergeKLists.ListNode list1, mergeKLists.ListNode list2) {
        if(list1 == null) {
            return list2;
        }
        if(list2 == null) {
            return list1;
        }
        if(list1.val < list2.val) {
            list1.next = mergeTwoLists(list1.next,list2);
            return list1;
        }else {
            list2.next = mergeTwoLists(list1,list2.next);
            return list2;
        }
    }

    public mergeKLists.ListNode mergeTwoLists(mergeKLists.ListNode list1, mergeKLists.ListNode list2) {
        if(list1 == null) {
            return list2;
        }
        if(list2 == null) {
            return list1;
        }
        mergeKLists.ListNode cur = new mergeKLists.ListNode(0);
        mergeKLists.ListNode ret = cur;
        while(list1 != null && list2 != null) {
            if(list1.val < list2.val) {
                cur.next = list1;
                list1 = list1.next;
            }else {
                cur.next = list2;
                list2 = list2.next;
            }
            cur = cur.next;
        }
        if(list1 == null) {
            while(list2 != null) {
                cur.next = list2;
                cur = cur.next;
                list2 = list2.next;
            }
        }
        if(list2 == null) {
            while(list1 != null) {
                cur.next = list1;
                cur = cur.next;
                list1 = list1.next;
            }
        }
        return ret.next;
    }
}
